A vertical bag forming, filling and sealing machine of the above-cited kind is known from EP-A-1052170. This known machine is a discontinuously operating machine according to which appropriate transport means cyclically move the wrapping material in the form of a flexible tube from above to below. Accordingly, especially during the inward movement of the weld jaws of the cross-seam welding device and the folding members of the folding device the wrapping material is not moved further on but is stopped so that the folding and welding steps can be carried out. Also in this position the filled tube bag is lifted relative to the folding device and the two folding members of the folding device are moved horizontally inward in order to press the wrapping material tightly against the upper surface of the filling.
The supplied wrapping material is pressed closely and tightly at the surface of the filling by the inward movement of the two folding members during the simultaneous lifting of the tube bag so that air present in this region of the tube bag is pressed out. Accordingly, no air cushion remains below the newly formed cross weld seam.
With this known vertical forming, filling and sealing machine good results are obtained. However, it is clear that this machine cannot produce large numbers of tube bags filled with filling per unit of time on account of its discontinuous operation.